Telephone plant



Sept, 13 1932. K. LARSSON ET AL; I 1,877,672 I TELEPHONE PLANT Filed May 26, 1931 2 Sheets-$heet 1 A5 5L QV l'l'l Sept. 13, 1932. K. LARSSON ET. AL

I TELEPHONE PLANT Filed May 26, 1951 2 Sheets-Sheet Patented Sept 13, 1932 xnur nansson AND NILS GUNNARPALMGREN, or STOGKHOLM, swsnnn, Assre'nons T0 TELEFONAKTIEBQLAGET. L. M. ERICSSON,

OE SWEDEN rnnnrnonn rrnnr Application filed May 26, 193i, Seria1INo.'54Q,15 8, and. in Sweden 31, 1930.

The present invention refers to such automaticand semi-automatic telephone systems which are provided with registers and in which the subscribers lines are connected to the: registers over call finders and appertaining cord linesin-sucha manner that each 7 call causes the startingof a plurality of call finders, the connection being established over that callfinder. which first findsthe calling subscribersline. More particularly the invention: referstosuch systems of: the latter kind innwhich each register, by meansot the cord'finder appertaining-to the register, first selects a call finder which is free for the time being. whereupon only the call finder thus'sel'ectedi isstar-ted for-the purpose of hunting for the calling subscr-ibers line.

Systems of this kind are known in which the starting circuitsot thecall finders as well as the impulse circuits of the register are adapted: tobe connected. to the call finders or the cord" lines respectivelyby means of the cord: finder appertaining to. the register. As

distinguishe dtfrom .thelatter system the present. invention. is. characterized in that the starting circuits. of the call finder and the impulse circuits of the registers are adapted to be selectively conneotedatothe call finders or: cord: lines respectively by. means of separate switching devices. Throughsucha dis-' tribution; ofi the starting circuits and. the

impulse circuitsto mutuallyv independent switchingmembers a greater latitude is gainedin regarditothe manner of arranging the switching. circuits, which; inturn. renders possible the simplification and reduction. of

1 cost-ofthe apparatus equipment: required for starting-the call finders and; connecting the registers into. circuit. The fact that the starting of the call finders takes place before the register ismade operative may, by way: of: example, bemade use of according to=the invention in such a manner that the requirement for a. special-cord finder for connecting-in thestarting circuits is. eliminated, in. that, for instance, an auxiliary apparatus appertaining to the register may be arranged to hunt: for andz start: an idle call findenbyv means of? a. preparatory switching madeoperative first after the register has been connected tothe cord line forthepuron s'rocxrrorn, swEnnN; A C MPANY poseot carrying out certainregulating tunctions. At the same time the switching mem- "bers required .for the switching-in of theimpulse circuits of the register may be simplified as they are not called'upon to carry out any selector function and may thus, by way of example, consist of relays appertaiir' ing to the difierent 'cord. lines.

The invention will be more closely "described with reference to the accompanying drawings. Figure 1 is a diagrammatic rep .resentation intended to illustrate the prin ciple of the invention, whereas Figure 2 shows a circuit diagram of an arrangement accordingto the invention.

Figure 1 illustrates diagrammatically a plu'ralityot cord lines SL with appertaining callfinders ASand groupselectors GV. All

cord lines are assumed to be accessible to one and the same group of subscribe'rs,:to which group also a number of registers RE belong. Ifthe group of. subscribers comprises, by way of example, 500 subscribers lines said group may be served by 8 registers. In the shown example said registers are distributed over.

the different cord'lines SL in such a. manner thateach register may: connect itself only to some of the cord lines appertaining to the subscribersgroupi Said cord lines are thus group G by means of a switching deviceKS.

Said switching-device maybe of arbitrary kind, for instance a cord line searcher. It may, also-consist ofrelays- On the drawing the small circles in the junction points between the different lines indicate theconnec- V tions whichmay be established by means of the difierent switching apparatuses. The lines BL represent those impulse circuits over which the registers are set and over which the setting of the selectors is controlled.

- The figurealso illustrates the arrangement 0f the starting circuits of the call "finders. ;operation, said; auxiliary apparatus being call-finderiASis provided .withfa. start-' f" apparatus are indicated by means of circles in the junction points between the different lines. The starting circuits also include contacts SK which are opened as soon as'the call finder is energized and, further, contacts RK which are disposed in the circuit branches -appertainmg to thedifferent registers and which are open when the appertaining regis '-ter is used and, finally, a contact TK adapted to be closed by a relay STR as soon as a call occurs, said relay being common to the whole group ofsubscribers. If upon a call the switching apparatuses SS are set on call findersiAS which are idle for the time being the starting circuits will be closed by means of the starting relays SR appertaining to said call finders over contacts RK of free registers. In case the call finder should be engaged the switching apparatus SS will immediately hunt for a free call finder and start the same. As long as a register is engaged none of the appertaining call finders can be all) ' each free register.

the corresponding cord line.

started. It is thus evident that each call causes the starting of only one call finder for As soon as a call finder is started the switching'apparatus KS may be actuated for the purpose of connecting the settingand control circuits of the register to Said connection into circuit does not necessarily include a selectiveswitching operation for the reason that the cord line has already been selected by the switching apparatus SS. For the connecting-in of the setting and control circuits of the register simple relays may therefore advantageously be used.

Figure 2 shows a simplified circuit diagram for a portion of a talking connection in an automatic telephone plant comprising a call finder AS, a group selector GV, and a register RE. The selectors are machine driven and of the kind, the contact arms Ka, K6, Ka of which have two setting movements in the same plane namely a turning movement for selecting a line group and a radial movement for. selecting a certain line. A fourth contact arm Kcl has only a turning movement. The motion mechanism is controlled in known manner by means of two switching magnets CVS and CBS of which the former brings about a turning motion and the latter a radial motion.

The parts appertaining to the register RE are enclosed within the dot and dash rectangle. The register is provided with four impulse receivers R R R R adapted to be set stepwise by means of the current impulses sent out from the subscriber. The register is also provided with an electromagnetically controlled auxiliary apparatus SS adapted to hunt for a free call finder and also to bring about the successive connecting into circuit of'the driving magnets RM 'RM RM RM of the impulse receivers R R R R to the impulse circuit controlled by the subscriber. For this purpose the auxiliary ap paratus SS is provided withjthree contact arms A A A disposed on the same shaft B, of which contact arms the first one, A controls the starting circuits of the call finders whereas the second, A controls the circuits for the switching magnet SM of the auxiliary apparatus, and the third A the circuits for the driving magnets'RM RM RM RM The contact arms are adapted ,to be set in 10 positions, of which the first one is the normal position- The driving mechanism consists of atoothed wheel 7 C disposed on the shaft B, aspringgactuated stepping pawl D engaging said toothed wheel, and aspring E which tends to turn the toothed wheel in the direction indicated by the arrow P, a stepwise motion. being imparted to the wheel in known manner under control of the electromagnet SM in such a way, that the contact arms are brought forward a half-step when the magnet SM attracts its armature F and a further half-step when the magnet SM drops its armature.

, The five first contact positions of the auxiliary apparatus SS are intended for the selection of a free call finderwhereas the following four contact positions are intended for the connecting-in of the different impulse receivers R R R B A plurality of relays -RR ,--RR RR serve to control the auxiliary apparatus for the purpose of hunting fora free call finder, whereas the continued motion .of the auxiliary apparatus occurs under the control of an impulse relay BB and two slowacting relaysRR and ER The connection. of the setting. and control circuits of'the register to the call line'SL is in the shown example effected by means of a a relay BN appertaining to the cord line.

The arrangement operates in the following mann'er. i

Upon a call from a subscriber AB a circuit '1 is closed over the subscribers .line L through a line relay LR which attracts its armature and connects test potential to the third wire of .the subscribers'lineover the contact 2. The line relay also closes at its contact 3 a circuit a for a relay LGR which "is common to the subscribers'lines connected to the same contact row in the call finder AS. The call finders are in this case assumed to have a capacity of 500 lines, the contacts a, b, 0 of which are disposed in rows with 20,contact groups in. each row. Simultaneously herewith'the test contact dappertainng; to; he sam ntact, now ob ains test pot ntial overt e contact 3 1 The elay LGB intern closc the cir uitjaf r a tartingvrelay STR Which is comm n toi l: su scribens incs h i dgz o p ques ion. When the latter relay attracts itsarmatnrethe: Starting circuit Gris closed'for one ofthe, call finders .belongingto each free register. Itmayinitially be assumed that the first of the call finders appertaining to the register RE is lfreefor thetimebeing. The circuit 6; is then closed directly over the contact arm; A inits, normal position. In said circuittlf e relay RR is included which at its.- contact 7, cuts out the relay RR whichis-slower than R111 attracting its armatureand therefore i on. this occasion remains inoperative, The

circuit 6. extends over a contact Sotthe-call finder, which contact is open 'When the call finder starts its radial motion, and over-a contact 9 of the group selector which is opened when the group selector leaves its normal position. It also includes the; starting relay of the call. finder which relay now attracts its armature and causes the starting of the call finder. i n :7. i

In case the first call finder shouldibei en gaged thecircuit, 6 4 is not 1 immediately established, but a circuit through the-relay- BB over the contact 7: and the common part of the circuit 6 is at first closed. Therelay RR is energized, thereby connecting the starting circuits for all call finders appertainingto the register in. question to the operative winding of the relay BB The latter will consequently b'e-energized, provided any one of the said call finders is free, the relay BB being then immediately again disconnected at the contact 10. The relay BB simul-V taneously connects. itself into holding circuit over its, contact 11.f W hen the relay RR attracts. its armature a circuit 12, is closed" through. the control, magnet, SM,; the

contact arms of the auxiliary apparatus being then brought. forward half astep The contact arm A then, makes contact with the contact 10 which. is connected tothestarting circuit of the other call finder. Thecircuit is however, simultaneously interrupted, as the contact, arm A now occupies an intermediate position between thecontacts: Z11 In consequence hereof thecontactarms are brought forward an ther halt-step, the

arm A then still making contactv with the contact Z2 whereas. the, armjA now makes contact with. the contact 70 In case also the other cell finder is engaged the control magnet SM now receives a current impulse over the Contact 70 whereby the contact arms are brought forward a further halfstep solthat the arm A makes contact with a contact k connected to the starting cirthen=encrgizedi openingzthe contact 1&3 imtlis I n ptedi-i Qonsequently the:- ones; arms nee main. in; their third. p0$1t 01li=- Si-mnltane ously herewiththe rela disconnectedcircuit; .152. which thus now-v. remains iinter nicase all otthe callifindels;appert ining.

motion, n rea i y a; p urali y of; all: findha e been arted imult o sly, as will Th seen from-, F ignre 1;. The. call; finder:v which first finds: he onta t: ow t which. e? calling: subs riber s nnect d=- will; then; e set br adi li motion wh e the Q lhQD 11ind' ens s pi in; ase sensual? all ioec n. contaet er,- he con ac new: in; question; a

circuit 15- is closedithrough a; est relayiRsize which attracts its; armature andeintcrrnpts he ir it v e-"tur ng motion o th icall' finder; then; stopping; Simultaneously; herewith the s erti gr lay: is ri'IZCIIi- -Q at the contact; 1.6 ozfi therelay BS1, the relay tinue their turning-mo ion When h cQQ tact: arm Kid-i make -1 contact With-1m est SR then; dropping its riar nature; andv closing 1 a cir uit. 1??? hro gh; hefswritching magne CBS whereby the: calli finder is started-1 in; a radial; ire i n; W en relay RS1 attracted its: arm ture it. s o t ircuitedi t; its-1 contact 18; a; counter-acting part of its; windinggso that theefi'ectivenumberrof am ,ree. turnsof he: elay was n re se iwhere yis guaranteed that the: re ay oes not. drop-its a mature on account. of: the; sh nting of tllegg e ay at -heztest ontact d whichloccursiwhen other:- call fin ers; pa s he ontact: row in question. At t e ame i e heicontactrow is hereby marked as engaged; forother call finders while the first, mentioned; call; finders; moves, in a rad-iali direction, for thewpurpose of: hunting for;- the calling; SubSriber s,.- line.

henthe call finder finds thecallingsubsombers: line a circuit; 19;- is closed; oven the third. wire; including; the; Onto-(iii; relay BRIofEil sarmature and in erruptisathe circuit at simultaneously herewith. The contact; 2- ofii the; relay ishowever; mai ainedro osed h oughtthe a tioni'ofi'the rel y: BB1; B1

. iclay RS interrupts theicircuitillf, the call 7 findenthen; stopping' on thei contacts: ofithe callin'g-lsubscriberis line. EheIeIay-(BSZMS ere: within the subscri rs group;iniquesticnfi' j short-circuits at it'scontact'go the; relay RS "which thus drops its armat'ure The circuit "19 is then kept closed over acontact 21 of the relay RS whereby at the a same time a part ofthe relay Winding is disconnected. The

relay RS' fialso closes; a circuit 22 through the connectingrelay BN of the register which-relay then= attracts its armature. and

in turn closes acircuit=23 extending over the subscribers line and including the; impulse "relay RR; which now attracts itsarmature.

Then a circuit '24 is closedvfo'r aslow-acting relay BB I which in turn closes a circuit '25 for the relayER which attracts its armature 'Meanwhile' the subscriberhas in known manner receiveda buzzer signal which indicates that the impulse sending may start.

-During the impulse sending the relay BB maintains its' armature attracted; l/Vhen the impulse relay 'RRgforth'e first time drops-its armature the circuit is closed for theslowacting relay BR which then attracts its arm- "ature 'and closes the circuit 31 for the control magnet SM, the auxiliary apparatus being then brought forward one half step. "Also in the 'newposition, however, the arm Ag remains in 'contact'with the contact Each time theimpulse relay RR, drops its armature-a current impulse is sent over the circuit 32-through the driving magnet RM for the impulsereceiverR which thereby-1s "set in accordance with the-first digit in the desired subscribe'rs number, At the end of 3 the first impulse series the-impulse relay BB remains current carrying and in consequence hereof the relay RR dropsits armature.

-Then the circuit 31 is interrupted and the contact arms ;of the auxiliary apparatus are brought forlwarda further half-step-to the *position 7 in which the contact arm A makes impu'lsejserie's will consequently set the im- -pulse receiver R2 At the end of the second contact with'the contact 11: .1 r The subsequent impulse series the contact arm A which at the beginning of said impulse series was brought forward a further half-step while maintaining contact with the contact I0 will *be brought forward totheposition 8 inwhich the impulse receiver R isconnectedinto'circuit, which impulse receiver thereafter is set 60 -connecting into circuitand setting of the fourth impulse receiver-R is eifected' in a by means of the third'impulse series'. The

similar manner while the contact ar m Ag remains in the ninth pos tion; When'the relay 83.) HR drops its armature after the sendingof the last impulse series the contact arms of, the auxiliary apparatus are brought forward a further half-step whereby the auxiliary apparatus reaches the tenthsetting position.

Hereafter the'setting of-group selectors and line selectors i-sefiected in a mannerhnown per se under contr'ol of the register. After completed setting of all the selectors included in the talking connection a'circuit 33 is closed through a relay BN which'attracts its armature and disconnects the connecting relay 3M whereby the register is released. At the sametime-the relay BN connectsitself over its contact crime the circuit 22 in place .o

of the relay'RN When finally the impulse relay RRyls deenergized the slow-acting relay BB receives a current impulse which is interrupted when the-relay 55 dropsits armature.

In consequence hereofalso the control magnet SM receives a further impulse whereby the auxiliary apparatus SS'is brough forward to the'sta-r'tin'g position; When the relay RR; 'drops its armature also the relay ER is demergiZedI The register-isnow ready for receiving a new call. Q

We claim: ,j" I 1 T 1. In a telephone system, a group of subscribers lines, a number of 'call'finders and cord lines allotted thereto, a number'of 'registers connectible to the said subscribers lines I over the'said cord lines and call finders, means to start upon a call a number of call finders "CQI I'BSPOHClIIIg to the number of registers free forthe time being, andswitchingmembers separate from the said starting means'to connect the impulse circuits of the registers to the cord lines.

2. A telephone system as'claimedin claim 1 in which the cord lines allotted'to the group 5105 of subscribers lines are divided into a numberof cord line groupsfthe registers appertai'ning to the subscribers group being allot tedto different groups of cord'lines.

3; In a' telephone system,.a group of sub-- scribers lines, a number of call finders and cord lines allotted thereto, a number of registers connectible tot-he said subscribers lines over'tlie'said cord lines and call finders, means to start'upon a call, a number of'call finders corresponding to the number of registers free for the time being, and a number of'relays separated from said starting means to connect I the impulse circuits of'the registers, to the cord lines. V

4:. a telephone system,a group of subscribers lines, a number of call finders and cord'lines allotted thereto, a number of regis- *ters'connectible'to the said subscribers lines over the said cord' lines and call finders, a-

.control switch all'otted to each register, which 5 control switch is adapted upon a call to'hunt 'for and start a free call finder, and switching members separate-"from the said control switch to connect-the impulse circuits ofthe 30 registers to the cord lines.

5. In a telephone system, a group of subscribers lines, a number of call finders and cord lines allotted thereto, a number of registers connectible to the said subscribers lines over the said cord lines and call finders, a switch allotted to each register, which control switch is adapted upon a call to hunt for and start a free call finder, a testing arrangement to prevent the starting of the said control switches when all finders appertaining to the register are engaged and switching members separate from the said control switch to connect the impulse circuits of the re isters to the cord lines.

11 testimony whereof we aflix our signatures.

KNUT LARSSON. NILS GUNNAR PALMGREN. 

